The present invention is directed to bicycles and, more particularly, to an apparatus for protecting electrical components associated with the bicycle.
Many electrical devices are available for use with bicycles. For example, lighting systems comprising a headlight, a taillight and other lighting elements often are used for night riding. Such lighting systems and other electrical equipment usually receive operating power from a battery or a dynamo. When a dynamo is used for the power supply, the voltage generated by the dynamo usually is proportional to the bicycle speed (wheel RPM). At high speeds, the generated voltage can sometimes exceed 100 V, so some kind of protection device is needed to prevent excessive voltage from being applied to the electrical components. Japanese Unexamined Patent Application (Kokai) No. 2204-88812 discloses a voltage protection device in the form of a bypass circuit comprising a Zener diode disposed between the dynamo and the load. When the voltage generated by the dynamo is over a certain threshold, current flows through the Zener diode so that the voltage applied to lamps and to other electrical equipment is limited to no more than a selected voltage level.
While the use of a bypass circuit such as a Zener diode can provide overvoltage protection for the electrical components, bypass circuits can produce some undesirable side effects. For example, the electrical current consumed by the electrical devices creates rotational resistance in the dynamo, and such rotational resistance adds to the pedaling effort required by the cyclist. Some dynamos, such as block dynamos, are activated only when needed to power the electrical equipment. Accordingly, those dynamos do not create pedaling resistance when the electrical equipment is not in use.
On the other hand, internal hub dynamos are built integrally with the wheel hub and always rotate together with the wheel. FIG. 1 is a schematic block diagram of a bicycle electrical component system that employs an internal hub dynamo and an overvoltage protection circuit. As shown therein, an overvoltage protection circuit 3 comprising a Zener diode is connected to the dynamo 2 of a wheel hub dynamo unit 1. Electrical components powered by such dynamos are turned on manually or automatically independently of rotation of the wheel. Electrical power is consumed by headlight 4 and taillight 5 whenever they are turned on, thus causing rotational resistance in rotation of the wheel hub. When headlight 4 and taillight 5 are turned off, overvoltage protection circuit 3 consumes all of the power that was consumed by headlight 4 and taillight 5 when those lighting elements were turned on. Thus, dynamo 2 always generates power and creates rotational resistance, thus resulting in unnecessary pedaling burden on the rider.